Oat-cell bronchial carcinoma. Identification of cells in pleural fluid.

An analysis is made of the accuracy of diagnosing oat-cell (small cell) carcinoma of the lung from the cytology of pleural fluid. All the material over a 22-year period has been reviewed. Air-dried smears were used, stained with May-Grünwald-Giemsa. Of 91 cases in which oat-cells were specified in the written report, 90 were either proved histologically to have oat-cell or anaplastic bronchial carcinoma, or else had clinical findings consistent with that diagnosis and were registered as having bronchial carcinoma at death. There was one false positive, and no false suspicious reports. Cytologic diagnosis of this tumor type has, therefore, been no less reliable than would be expected from a histologist examining a surgical biopsy of infiltrated tissue. Of 49 consecutive cases histologically proved to have oat-cell carcinoma, and with pleural effusions examined in this laboratory, 21 showed no malignant cells (43 per cent false negative). Diagnostic features and causes of error are discussed, as well as the advantage of air-dried smears over the standard Papanicolaou method for the detection of this cell type.